1. Field of the Invention
This invention relates in general to the field of temperature control and more particularly to an improved apparatus and method of providing temperature control to electronic devices using power following feedback.
2. Description of Related Art
The present invention relates to temperature control systems which maintain the temperature of an electronic device at or near a constant set point temperature while the device is being operated or tested. Two examples of electronic devices which are best operated at a constant or near constant temperature are packaged integrated chips and bare chips which are unpackaged. Maintaining the chip temperature near a constant set point is not difficult if the power dissipation of the chip is constant or varies in a small range while operating or testing. One way of handling such a situation is to couple the chip through a fixed thermal resistance to a thermal mass which is at a fixed temperature. But if the instantaneous power dissipation of the chip varies up and down in a wide range while operating or testing, then maintaining the chip temperature near a constant set point is very difficult.
Various temperature forcing systems are used to respond to the chip""s temperature variation caused by widely varying power dissipation of the chip. Feedback methods are commonly used to sense the varying temperature. Typical approaches involve the use of a temperature sensing device such as a thermocouple, mounted on the chip package or chip itself. Another approach is to integrate a temperature sensing device, such as a thermal diode, into the chip circuitry. Such a temperature sensing device would be used to sense changes in the chip""s temperature, and then adjust the temperature forcing system appropriately.
There are several problems with the use of temperature sensing devices. In the case of packaged chips, an externally mounted thermocouple will indicate the temperature of the package surface, not the temperature of the chip inside the package. At some level of power dissipation, this temperature difference will be significant to the test result. The use of temperature sensors integrated into the chip itself addresses this problem, but raises other issues. It is not typical practice for the chip manufacturer to integrate temperature sensors on the chip. Even if it were, each chip""s temperature sensor would have unique calibration requirements. All of the above present problems for high volume chip manufacturing.
Temporary temperature sensors, such as thermocouple probes, included in automated test handling equipment can address some of these issues. However, the package temperature vs. die temperature problem will remain. Also, the reliability of the temporary temperature sensor introduces error which can be significant to the high volume chip manufacturing test result. Moreover, the surface available for temperature control is the same surface needed for the temporary temperature sensor, complicating the problem further.
Therefore, a need has arisen for an apparatus and method of temperature control for electronic devices which can respond to the temperature of the electronic device, instead of the package. A further need exists for an apparatus and method of temperature control for electronic devices which can conveniently be used for high volume chip manufacturing. A further need exists for an apparatus and method of temperature control for electronic devices which is reliable. A further need exists for an apparatus and method of temperature control for electronic device which does not require significant surface area of the electronic device. A further need exists for a method of temperature control for electronic devices which does not require temperature sensing devices to be integrated into the chip or to be temporarily in contact with the chip. A further need exists for a method of temperature control for electronic devices which does not require collecting, maintaining, and applying the use of chip power profiles, and does not require the capability of performing such tasks in the automated test equipment, temperature forcing system, and testing software.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set out above.
Briefly, in accordance with one aspect of the present invention, a method for controlling a temperature of a device during testing with a thermal controller and a heat exchanger includes measuring an instantaneous power consumption of the device during testing, and controlling the heat exchanger with the thermal controller using the measured instantaneous power consumption by the device to regulate the temperature of the device during testing, wherein the heat exchanger is in conductive contact with the device.
In another aspect of the present invention, the device is an integrated circuit device.
In yet another aspect of the present invention, the heat exchanger is conductively coupled to the device, the heat exchanger being responsive to changes in the measured instantaneous power consumption by the device to regulate the temperature of the device.
In a further aspect of the present invention, the heat exchanger comprises a heat sink having a surface on which a heater element is incorporated, the heat sink removing heat from the device when the temperature of the device exceeds a temperature below a predetermined set-point temperature, and the heater element is controlled based on the measured instantaneous power consumption by the device to selectively introduce heat to maintain the device near the predetermined set-point.
In yet a further aspect of the present invention, measuring an instantaneous power consumption includes measuring the current provided to the device while the device is being tested.